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Vol. LXVI, No. 2
January 17, 2014

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NIDDK Researchers Chronicle Advances Against Sickle Cell Anemia, Diabetes

NIDDK director Dr. Griffin Rodgers (l) and scientist emeritus Dr. Peter Bennett at Grand Rounds
NIDDK director Dr. Griffin Rodgers (l) and scientist emeritus Dr. Peter Bennett at Grand Rounds

At a recent Clinical Center Grand Rounds, NIH researchers reviewed progress made against two major causes of illness and death. NIDDK scientist emeritus Dr. Peter Bennett discussed his work over the past five decades identifying risk factors for type 2 diabetes in Arizona’s Pima Indian community and NIDDK director Dr. Griffin Rodgers described advances against sickle cell anemia.

Sickle cell anemia is a hereditary blood disorder that primarily affects people of African, Middle Eastern and Indian descent. The condition affects hemoglobin, a protein found in red blood cells, explained Rodgers. Those with sickle cell anemia produce C-shaped red blood cells that clog small blood vessels, causing oxygen deprivation, pain and organ damage.

Rodgers began the discussion. “Arguably, we know more about sickle cell anemia than we do about any other disease currently known to man,”
he said.

He and his colleagues study the effects of hydroxyurea, the first FDA-approved therapy for sickle cell anemia, which Rodgers helped develop in the 1990s. The drug activates the production of fetal hemoglobin, which effectively interferes with the aggregation of sickle hemoglobin inside red blood cells. The resulting inhibition of the “sickling” process alleviates painful episodes associated with sickle cell anemia. “Although hydroxyurea lessens many complications, it really isn’t a cure for sickle cell disease,” he said.

Results from a recent clinical trial at NIH suggest that a cure for sickle cell anemia may be possible. In nine of 10 adults who had been severely affected by sickle cell anemia, a stem cell transplant reversed the disease. A cure would require replacing bone marrow of patients with sickle cell anemia with bone marrow stem cells from a healthy sibling. However, the treatment doesn’t work for everyone. “Within this population, we estimate that only 25 or 30 percent of patients have eligible siblings,” said Rodgers.

He said it is possible that advances in stem cell gene therapy will one day allow everyone with sickle cell anemia to benefit from the treatment.

Next, Bennett spoke about type 2 diabetes in the Pima Indians of Arizona. He was chief of NIDDK’s intramural Phoenix Epidemiology and Clinical Research Branch, which began conducting cooperative research efforts with the Pimas in 1963, after scientists discovered the high prevalence of obesity and type 2 diabetes in this population.

For over 30 years, Bennett administered glucose tolerance tests to almost every Pima Indian age 5 or older. Test results showed the Arizona Pima Indians had the highest prevalence of type 2 diabetes of any group in the world—including the genetically similar Mexican Pima Indians—leading Bennett to conclude that environmental factors play a role in the prevalence of type 2 diabetes. He found that low physical activity and obesity were risk factors for the disease. Later, he found insulin resistance was another risk factor. All of these findings applied far beyond the Pima population.

He also found that children whose parents had diabetes were likelier to develop the disease earlier in life and that breastfeeding prevented the development of diabetes by almost 60 percent. Bennett’s achievements in the field of diabetes research continue to be the foundation for the prevention, diagnosis and treatment of type 2 diabetes.

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