7568 Sickle Cell Variant Promotes Glycemic Dysregulation In A Mouse Model Of Human Sickle Cell Trait And Sickle Cell Disease

Abstract

Abstract Disclosure: J.L. Zapater: None. B.T. Layden: None. Since cases of type 2 diabetes mellitus (T2DM) are rising due to environmental and societal factors, it is estimated that in the coming decades that T2DM will affect twenty percent of the United States population and that mortality from diabetic complications will continue to rise. It is therefore critical to accurately diagnose and treat T2DM early, however this proves difficult in certain populations. Sickle cell anemia is a common hemoglobinopathy in which changes in red blood cell turnover lead to inaccurate measurement of hemoglobin A1c and incongruencies between this and other glucose measures, making it difficult to establish a diagnosis of T2DM. The sickle cell variant has been linked to higher hemoglobin A1c, and with 1-in-10 African Americans having the sickle cell trait (SCT), an increasing prevalence of sickle cell disease (SCD), and a higher risk of diabetic complications in those with SCT or SCD, it is critical that we elucidate the precise mechanisms by which the sickle cell variant affects glycemic homeostasis. In this work, we utilized a mouse model of human sickle cell anemia to begin to determine the biochemical mechanisms governing glucose handling in the presence of the sickle cell variant by examining glycemic homeostasis under normal and obesogenic conditions. Townes sickle cell mice containing human hemoglobin with either two normal β-globin chains (littermate controls) or one normal and one sickle β-globin chain (SCT) were placed on either a normal chow diet or on a high fat diet (HFD) until 20 weeks of age to induce an obesogenic state. Although no overt glycemic phenotype was noted, 20-week-old HFD-fed SCT mice exhibited an increased glucose excursion following an oral glucose load compared to littermate controls. Though serum insulin levels were comparable, HFD-fed SCT mice also exhibited a reduced whole-body insulin sensitivity during insulin tolerance testing compared to controls, correlating with the noted increased glycemic excursion. With these findings, we have initiated work with Townes mice containing two normal α-chains and two sickle β-chains (SCD), which is found in human sickle cell anemia. Early results show that chow-fed SCD mice exhibit greater random and fasting glucose levels at 8 and 12 weeks of age, despite similar fasting insulin levels. These findings suggest that the presence of one sickle β-globin chain, as in SCT, promotes hyperglycemia in the obesogenic state through reduction of whole-body insulin sensitivity. Furthermore, the presence of two sickle β-globin chains, as in SCD, is sufficient to dysregulate glycemic control under normal conditions. In total, these findings demonstrate that the presence of the sickle cell variant promotes glucose dysregulation and hyperglycemia, meaning that it is essential to understand the glycemic regulation in patients with sickle cell trait and sickle cell anemia. Presentation: 6/1/2024