Preface

*Adipose Tissue—An Update* is an update to the first volume, which was published by IntechOpen in 2018, and a part of the book series "Physiology." The chapters include information on adipose tissue such as the characterization of this tissue, the role of sirtuins in its metabolism, and its role in diseases. The book also includes a description of adipose tissue as an endocrine organ, as well as a signaling system in this tissue. This book is an important source of information because it describes several aspects of adipose tissue. Based on the interest of readers, IntechOpen decided to continue the publication of books on adipose tissue. Therefore, *Adipose Tissue— An Update* is the result of this continuation.

Adipose tissue is a kind of specialized connective tissue. Depending on its type, adipose tissue plays different and significant roles in humans and animals. For example, brown adipose tissue, which is found in fetuses and newborn, in adult humans is practically absent; in mammals it is involved in the process of thermogenesis, metabolizing fatty acids. White adipose tissue has different functions. It protects against environmental factors that can cause mechanical injury and cold. Other functions include the storage of lipids and triacylglycerol and the synthesis of fatty acids. During fasting, fatty acids are released and in the process of β-oxidation are a source of adenosine triphosphate. White adipose tissue is also a major secretory organ. White adipose tissue secretes bioactive molecules such as cholesterol, retinol, steroid hormones, prostaglandins, and proteins known as "adipokines" that influence human physiology and pathology. These molecules have a beneficial role. Unfortunately, they may also be associated with pathologies and diseases such as obesity and insulin resistance. They may increase the risk of metabolic syndrome, cardiovascular diseases, and others. Obesity, due to visceral accumulation of adipose tissue, is especially dangerous. It is suggested that release of fatty acids from the visceral depot into the portal vein increases gluconeogenesis and hepatic glucose output, causing insulin resistance. Insulin resistance, on the other hand, may cause type 2 diabetes mellitus. The World Health Organization defined type 2 diabetes mellitus as "a progressive worldwide epidemic." Visceral abdominal obesity reduces life expectancy by about 8 years. Beige adipose tissue histologically is similar to brown adipose tissue. Stimuli, such as cold, exercise, or thyroid hormones, cause differentiation of white adipose tissue into brown adipose tissue. This process is an adaptive and reversible response of white adipose tissue to stimuli.

In the past several decades, knowledge of adipose tissue has been rapidly growing. This book aims to provide an overview of the topics of adipose tissue and its role in human physiology and pathology. The book is written by authors from different laboratories, yet the editor has tried to arrange the chapters in an issue order to make it easier for readers to find what they need. The authors discuss adipose tissue from different aspects and hope to enhance a clear understanding of this histological, physiological, and pathological problem.

This book contains three sections focusing on the topic of adipose tissue. Section 1 contains only one chapter and presents the general characteristics of adipose tissue. Section 2, which includes Chapters 2–4, mainly describes the role of sirtuins, follistatin, and alcohol in the metabolism of adipose tissue. Finally, Section 3, which includes Chapters 5–7, focuses on the disorders in adipose tissue and their influence on human health and diseases.

I hope that this book will be of help to scientists, doctors, pharmacists, and other experts in various disciplines. It should also be suitable for teaching.

I would like to thank Ms. Marina Dusevic for her great effort in book planning and editing during the process of book publication.

> **dr. hab. Leszek Szablewski** Professor, Medical University of Warsaw, Warsaw, Poland

> > **1**

Section 1

General Characteristics of

Adipose Tissue

### Section 1
