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

Xiaobo Lin, Lina Ma, Robin L. Fitzgerald, Richard E. Ostlund

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

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]d-chiro-inositol (DCI) by 159-fold. [3H]myo-Inositol uptake increased by 37-fold. In contrast, [14C]d-glucose, [14C]2-deoxy-d-glucose, or [14C]3-O-methyl-d-glucose uptake remained unchanged in the presence of either 0, 5.5, or 25 mM unlabeled glucose. The Km of DCI and myo-inositol for DCI uptake was 111.0 and 158.0 μM, respectively, whereas glucose competed for DCI uptake with a Ki 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.

Original languageEnglish
Pages (from-to)197-201
Number of pages5
JournalArchives of Biochemistry and Biophysics
Volume481
Issue number2
DOIs
StatePublished - Jan 15 2009

Keywords

  • DCI
  • Diabetes
  • Glucose
  • Insulin resistance
  • PCOS
  • Pinitol
  • SMIT2
  • d-chiro-Inositol
  • myo-Inositol

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