The nerve of that adipose tissue

Neuroendocrinology of Leptinedited by Ehud Ur. Karger, Basel, 2000.CHF 169.00, DEM 202.00, $147.00 (x + 129 pages)ISBN 3 8055 6921 1The recent discovery of leptin as the product of expression of the obese gene (LEP) has resulted in an explosion of research activity that has broadened our understanding of the role of leptin and downstream factors in obesity, and aided the discovery of novel factors involved in obesity. Neuroendocrinology of Leptin seems to be the first published book about leptin. Although short, not thicker than your index finger (129 pages), this book is a valuable reference for neuroendocrinologists, reviewing, in eight chapters, several aspects of neuroendocrinology and the relationship of leptin to neuroendocrinology.In the first chapter, L.A. Campbell reviews ‘The Neurobiology of Leptin’. The term ‘Ob protein’ persists as a synonym that is used interchangeably with leptin. This chapter is somewhat introductory in nature, including the fundamental physiology related to leptin, and discussion of obesity and the leptin receptor. The genetics of obesity and the interaction of leptin with other hormones, particularly neuropeptide Y (NPY), are introduced.The second chapter, ‘Central Mechanisms Responsible for the Actions of Ob Protein (Leptin) on Food Intake, Metabolism, and Body Energy Storage’ (also by Campbell), discusses the regulation of energy expenditure by using animal models of obesity, which have been so important in our preliminary studies in the area of leptin physiology. Other sections include actions of the Ob protein, in both rats and mice, on appetite and metabolic rate, and on the effect of leptin in obesity. The topic of leptin resistance is introduced although the term per se is not used in this chapter.J.K. Elmquist is the author of the short third chapter ‘Anatomic Basis of Leptin Action in the Hypothalamus’, which covers the relationship between leptin and hypothalamic hormones, and reviews pituitary endocrinology and distribution of leptin receptors in the brain. There are also specific sections on the major hypothalamic centers, including discussions about how leptin interacts with each of these centers.In ‘Leptin and the Neuroendocrinology of Fasting’ (the fourth chapter), R.S. Ahima introduces the responses to fasting and starvation. This includes discussion of the interactions between leptin and other hormones, such as adrenal corticoids, thyroid hormones and insulin. In addition, the role of leptin as both a sensor and a signal to the hypothalamus and pituitary is presented.The next chapter, by Mobbs and Mizuno, is entitled ‘Leptin Regulation of Proopiomelanocortin’. Other genes involved in obesity include those encoding agouti, α-melanocyte-stimulating hormone and proopiomelanocortin (POMC), and this chapter covers the interaction of leptin with the products of some of these genes. It also includes a discussion of the interaction of leptin with β-endorphin and the role of this interaction in leptin physiology. Leptin increases production of hypothalamic POMC mRNA and seems to play an important role in stimulating other areas of physiological regulation. This is certainly an important topic with respect to our understanding of leptin involvement in the hypothalamus and pituitary.Chapter six, authored by Widdowson and Wilding, is specifically related to ‘Hypothalamic Neuropeptide Y and its Neuroendocrine Regulation by Leptin’. NPY is the most studied and perhaps most important regulator of satiety, and there is extensive early literature in this area. This chapter covers the physiological role of NPY, as well as NPY receptors and the localization of NPY in the hypothalamus. In this chapter, a section on leptin discovery and the effects of leptin on the brain serves as a fundamental review, which is followed by coverage of the leptin–NPY interaction.The next chapter by Cheung, Clifton and Steiner covers ‘Leptin as a Metabolic Signal for the Onset of Puberty’. This chapter is probably the best written in the book and covers the specific area of physiological regulation where leptin might exert its effect on the hypothalamus and pituitary. The authors cover such aspects as nutrition in puberty and leptin in reproduction, and specific sections on the role of leptin in pubertal development (specifically in the rat, mouse, monkey and human) are included. The role that leptin plays in pubertal development, and whether leptin is permissive or causative, remain to be determined. However, this chapter presents the information very well and contains an excellent bibliography for those interested in this field.The last chapter, by Wilkinson, Morash and Ur, presents the novel topic of ‘The Brain as a Source of Leptin’. Although leptin was first identified as a product of white adipose tissue, it is now recognized that other sites in the body, most notably the placenta, also produce leptin. This chapter reviews evidence for the production of leptin by the brain itself. Mechanisms of leptin transport into the brain and, indeed, whether leptin needs to be transported into the brain, are discussed. The role of leptin in cellular activation through the expression of FOS and other regulatory agents, and the localization of leptin in rat and mouse brain using immunochemical detection, are also presented. The authors obviously wish to add brain and pituitary to the list of tissues that produce leptin.The broad understanding of leptin physiology has increased tremendously in recent years. This book is an initial introduction to the topic and plays an important role in providing basic information in the form of a well-organized compendium. I trust that other volumes on additional areas of leptin physiology will follow. Although several chapters could have been improved by the inclusion of additional references, this volume will be invaluable to neuroendocrinologists, as well as to anyone interested in leptin physiology and even endocrinology in general. The text is short, very readable and should be on every leptin physiologist's bookshelf, if not that of every endocrinologist. It was a delight to be able to read the first published book devoted to leptin.