Human sodium/inositol cotransporter 2 (SMIT2) transports inositols but not glucose in L6 cells

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• 作者：Xiaobo Lin ; Lina Ma ; Robin L. Fitzgerald ; Richard E. Ostlund Jr.
• 关键词：SMIT2 ; d-chiro-Inositol ; myo-Inositol ; Insulin resistance ; Diabetes ; PCOS ; DCI ; Glucose ; Pinitol
• 刊名：Archives of Biochemistry and Biophysics
• 出版年：2009
• 出版时间：15 January 2009
• 年：2009
• 卷：481
• 期：2
• 页码：197-201
• 全文大小：343 K

文摘

To characterize the function of the sodium/inositol symporter SMIT2 in skeletal muscle, human SMIT2 cDNA was transfected into L6 myoblasts using pcDNA3.1 expression vector. Compared with the pcDNA3.1 vector only transfection, this overexpression increased the uptake of [³H]estyle value=""smcaps"">d-chiro-inositol (DCI) by 159-fold. [³H]myo-Inositol uptake increased by 37-fold. In contrast, [¹⁴C]estyle value=""smcaps"">d-glucose, [¹⁴C]2-deoxy-estyle value=""smcaps"">d-glucose, or [¹⁴C]3-O-methyl-estyle value=""smcaps"">d-glucose uptake remained unchanged in the presence of either 0, 5.5, or 25 mM unlabeled glucose. The K_m of DCI and myo-inositol for DCI uptake was 111.0 and 158.0 μM, respectively, whereas glucose competed for DCI uptake with a K_i of 6.1 mM. Insulin treatment of non-transfected L6 cells (2 μM for 24 h) increased [³H]DCI specific uptake 18-fold. DCI transport is up regulated by insulin and competitively inhibited by millimolar levels of glucose. Therefore, expression and/or function of SMIT2, a high affinity transporter specific for DCI and myo-inositol, may be reduced in diabetes mellitus, insulin resistance and polycystic ovary syndrome causing the abnormal DCI metabolism observed in these conditions.