Insulin receptor cleavage induced by estrogen impairs insulin signaling.

INTRODUCTION: Soluble insulin receptor (sIR), which is the ectodomain of insulin receptor (IR), is present in human plasma. Plasma sIR levels are positively correlated with blood glucose levels and negatively correlated with insulin sensitivity. An in vitro model of IR cleavage shows that extracellular calpain 2 directly cleaves IR, which generates sIR, and sequential cleavage of the IRß subunit by γ-secretase impairs insulin signaling in a glucose concentration-dependent manner. Nevertheless, sIR levels vary among subjects with normal glucose levels. RESEARCH DESIGN AND METHODS: We examined sIR levels of pregnant women throughout gestation. Using an in vitro model, we also investigated the molecular mechanisms of IR cleavage induced by estradiol. RESULTS: In pregnant women, sIR levels were positively correlated with estrogen levels and significantly increased at late pregnancy independent of glucose levels. Using an in vitro model, estrogen elicited IR cleavage and impaired cellular insulin signaling. Estradiol-induced IR cleavage was inhibited by targeting of calpain 2 and γ-secretase. Estrogen exerted these biological effects via G protein-coupled estrogen receptor, and its selective ligand upregulated calpain 2 expression and promoted exosome secretion, which significantly increased extracellular calpain 2. Simultaneous stimulation of estrogen and high glucose levels had a synergic effect on IR cleavage. Metformin prevented calpain 2 release in exosomes and restored insulin signaling impaired by estrogen. CONCLUSIONS: Estradiol-induced IR cleavage causes cellular insulin resistance, and its molecular mechanisms are shared with those by high glucose levels. sIR levels at late pregnancy are significantly elevated along with estrogen levels. Therefore, estradiol-induced IR cleavage is preserved in pregnant women and could be part of the etiology of insulin resistance in gestational diabetes mellitus and overt diabetes during pregnancy.

A case of myelodysplastic syndrome with t(10;18)(q26;q21).

An 82-year-old male was admitted. Pancytopenia, a slightly low white blood cell count (3400/µL), and low levels of red blood cells (2.65 × 106/µL), hemoglobin (10.4 g/dL), and platelets (118,000/µL) were observed. Bone marrow aspiration was performed, revealing hypocellular bone marrow and normal blast levels (0.6%) with no dysplasia. G-banding chromosome analysis revealed the karyotype 45,X,-Y[3]/45, idem, t(10;18)(q26;q21)[13]/46,XY[4]. The patient was diagnosed with myelodysplastic syndrome, unclassified (MDS-U). This is the first case report demonstrating a patient with the chromosomal translocation, t(14;18)(q32;q21), which is extremely rare. This chromosomal aberration was critical for the diagnosis of MDS in this patient.

Rapid diagnosis of mixed phenotype acute leukemia after identifying a blood histogram abnormality.

A 38-year-old woman was suffering from back, right arm, and ankle joint pain, and visited our emergency department. Upon admission, the white blood cell (WBC) count was high (11,700/µL), and low numbers of red blood cells (2.21 × 106/µL) and platelets (PLTs) (42,000/µL) were observed. A PLT histogram showed an abnormally shaped peak at around 20-30 fL, suggesting the presence of giant PLTs or PLT aggregation. The WBC histogram showed abnormal elevation at 35 fL and around 100 fL, suggesting abnormal cells including nucleated red blood cells. A peripheral blood smear was prepared, and morphology was examined. As a result, blasts (4%) including many orthochromatic erythroblasts (48/100 WBCs) were observed. Acute leukemia was suspected, and the patient was transferred the next day to a hospital with a hematology department. Bone marrow aspiration revealed that 99% of cells were blasts positive for B lymphoid lineage markers and myeloperoxidase. The patient was diagnosed with mixed phenotype lineage acute leukemia, treated immediately, and achieved remission. Thus, careful observation of histogram abnormalities of an automatic blood cell analyzer is important for rapid diagnosis of acute leukemia.