Involved in the sodium-dependent cotransport of myo-inositol (MI) with a Na(+):MI stoichiometry of 2:1. Exclusively responsible for apical MI transport and absorption in intestine. Can also transport D-chiro-inositol (DCI) but not L-fructose. Exhibits stereospecific cotransport of both D-glucose and D-xylose. May induce apoptosis through the TNF-alpha, PDCD1 pathway. May play a role in the regulation of MI concentration in serum, involving reabsorption in at least the proximal tubule of the kidney. Highest expression in heart, skeletal muscle, kidney, liver and placenta. Weaker expression in brain, colon, spleen, lung and peripheral blood leukocytes. Acts as an autoimmune modifier in systemic lupus erythematosus (SLE) as it is significantly associated with low complement component 4 (C4), anti-Smith antibody, serositis, and alopecia. Belongs to the sodium:solute symporter (SSF) (TC 2.A.21) family.