Preface

Chapter 7 **Thyrotropin-Releasing Hormone (TRH) a Small Molecule in**

Luo

**VI** Contents

**Pancreas Promotes Insulin Producing Cell Proliferation 155** John Z.Q . Luo, Souriya Vang, Zhao Ting, Ivor Jackson and LuGuang

> At least one in ten people today are destined, on current trends, to develop diabetes at some point during their lifetime. The total number of individuals with diabetes worldwide is scheduled to double in a generation. WHO has defined type 2 diabetes mellitus, a progres‐ sive worldwide epidemic. The statistics are alarming: 30 million people were diagnosed with diabetes worldwide in 1985. By 1995, the number had risen to 135 million. It has been estimated that by 2010, 220 million people worldwide will be affected by the disease, and there will be some 300 million by the year 2015 as predicted by WHO. According to another statistics, the prevalence of all forms of diabetes is estimated to be 2–3% of the world's popu‐ lation, with the number of diabetic patients increasing by 4–5% per annum. Moreover, many people with diabetes remain undiagnosed.

> Type 1 diabetes is observed in approximately 5–10% of patients with diabetes mellitus. The incidence of type 1 diabetes is projected to increase 40% between 1997 and 2010. The studies suggest an annual global increase of 3–4% with the highest increase expected in the 0–4 year age group.

> The progress in molecular biology, genetics, epidemiology and in clinical applications not‐ withstanding, much more needs to be done. It will be of great importance to identify the molecular mechanisms of diabetes and insulin resistance.

> Most tissues and organs, such as the brain, need glucose constantly, as an important source of energy. The low blood concentrations of glucose can cause seizures, loss of consciousness, and death. On the other hand, long lasting elevation of blood glucose concentrations can result in blindness, renal failure, cardiac and peripheral vascular disease, and neuropathy. Therefore, blood glucose concentrations need to be maintained within narrow limits. The process of maintaining blood glucose at a steady-state level is called glucose homeostasis. This is accomplished by the finely hormone regulation of peripheral glucose uptake (glucose utilization), hepatic glucose production and glucose uptake during carbohydrates ingestion.

> Glucose is obtained directly from the diet and by the synthesis from other substances in or‐ gans such as liver. Glucose derived from the diet is transferred from the lumen of small in‐ testine, and both dietary glucose and glucose synthesized within the body have to be transported from the circulation into target cell. Glucose cannot penetrate the lipid bilayer, and specific carrier proteins are required to its diffusion. These transporters comprise two structurally and functionally distinct groups, whose members have been identified over the past decades, namely: the Na+ -dependent co-transporter (SGLT) and the facilitative, Na+ -in‐ dependent sugar transporters (GLUT). These various transporters exhibit different substrate specificities, kinetic properties and tissue expression profiles.

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 readers to find what they need.

Section 1, which includes chapters 1-2, mainly describes the Na+ -dependent co-transporter (SGLT) and facilitative, Na+ -independent glucose transporters (GLUT) and the important role of GLUT 4 in glucose homeostasis.

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 cells.

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

> **Dr. Leszek Szablewski** Chair of General Biology & Parasitology Center of Biostructure Research Medical University of Warsaw Poland

**Section 1**

**Glucose Transporters**
