**Glucose Transporters**

The book entitled "Glucose Homeostasis" edited by Dr. Leszek Szablewski provides a broad overview of the molecular, biochemical, and clinical aspects of glucose metabolism, insulin resistance and diabetes mellitus. The chapters will make the reader acquainted with a varie‐ ty of topics ranging from glucose transporters, glucose homeostasis and influence of adipo‐ kines and TRH on cells. This book is written by authors from different laboratories, yet, the editor has tried to arrange the book chapters in a single volume to make it easier for the

Section 2, which includes chapters 3-5, describes the mechanisms of glucose homeostasis.

Section 3, which includes chapters 6-7, describes the influence of adipokines and TRH on

This book will be of help to scientists, doctors, pharmacists, and other experts in various


**Dr. Leszek Szablewski**

Poland

Chair of General Biology & Parasitology

Center of Biostructure Research Medical University of Warsaw


Section 1, which includes chapters 1-2, mainly describes the Na+

readers to find what they need.

(SGLT) and facilitative, Na+

cells.

VIII Preface

disciplines.

role of GLUT 4 in glucose homeostasis.

**Chapter 1**

**Mammalian Sugar Transporters**

Additional information is available at the end of the chapter

(SGLTs) and glucose transporters (GLUTs), respectively.

(GLUT13) belong to the Class III [3].

for this cotransporter family is maintained by Na+/K(+)-ATPase [1].

dominant mechanism for glucose reuptake by the kidney (Figure 3A).

The various members of the GLUT protein family is comprised of 14 isoforms [2]

Glucose represents the major energy source of mammalian cells. Due to its hydrophilic nature, glucose requires specific transporters in order to cross cellular membranes. Such transport is, in the case of glucose and also other monosaccharides, mediated by energy-coupled as well as facilitative mechanisms represented by protein families of sodium-driven sugar cotransporters

SGLT cotransporter family present highly diverse functions. They cotransport Na+ with glucose (SGLT1, SGLT2, SGLT4, SGLT5), or galactose (SGLT1, SGLT5) or mannose (SGLT5) or fructose (SGLT5) but also with myoinositol (SGLT6, SMIT), with iodine (NIS) or with choline (CHT). One family member is not a transporter but a glucose sensor (SGLT3). Na+ gradient

The GLUT protein family consists of three different families that can be distinguished based on their protein sequence homologies: Class I comprises the classical transporters GLUT1-4 as well as the gene duplication of GLUT3 which is GLUT14, Class II contains the isoforms GLUT5, 7, 9, and 11, while GLUT6, 8, 10, 12 and the proton-driven myo-inositol transporter HMIT

Current understanding of whole body glucose homeostasis under normal-and, more impor‐ tantly, under disease conditions-is directly linked to the understanding of SGLT and GLUT physiology (Figure 1). The active mechanism of glucose (as well as galactose) absorption in the intestine is primarily catalysed by SGLT1 (Figure 3B), while SGLT2 represents the pre‐

> © 2014 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Robert Augustin and Eric Mayoux

http://dx.doi.org/10.5772/58325

**1. Introduction**
