Current interest in lipoprotein deficiency states stems from the growing realization of their importance in the etiology of premature coronary heart disease. While hypercholesterolemia and coronary heart disease risk are strongly correlated in their etiologic relationship, it is becoming equally clear that deficiencies in HDL, whether congenital or acquired, also enhance the risk for the future development of coronary atherosclerosis. This has led to renewed attention to the lipid hypothesis and realization of the fact that each lipoprotein class and apoprotein species has specific functions in the transport and cellular uptake of various lipids. It is a truism that a biochemical correlate of disease once identified is subsequently recognized with increasing frequency in clinical medicine. The story of HDL was no exception. Indeed hypoalphalipoproteinemia appears to be a disease of high prevalence approaching and perhaps even exceeding that of familial hypercholesterolemia.

Its clinical significance escaped our notice for many years largely due to a heavy emphasis on hypercholesterolemia and to difficulties in measuring HDL reliably. Recognizing that clinical assessment of patients suspected of lipoprotein disorders requires understanding of newer concepts, we thought it timely to assemble leaders in this field to highlight advances in understanding the lipoprotein deficiency syndromes and their etiologic mechanisms. The four chapters of this book represent areas of major interest. We have avoided the historic context and emphasized relationships between lipoprotein deficiencies, their molecular mechanisms and clinical correlations. The first chapter focuses on the relationship between plasma HDL deficiency and atherosclerosis. Clinically relevant relationships are identified, and various disease states commonly associated with premature coronary disease are covered.

Hypoalphalipoproteinemia is not a single disease but a multitude of syndromes with varied etiologies. The second chapter explores these syndromes discussing both the common autosomal dominant disorder and rare, mostly recessive, diseases differing in molecular etiologies. In chapter three lecithin: cholesterol acyl-transferase (LCAT), the enzyme responsible for plasma cholesterol esterification is discussed in detail. The role of LCAT in the context of cellular cholesterol efflux is also addressed. Numerous hypertriglyceridemic syndromes are associated with deficiencies of defects in lipoprotein lipase or hepatic lipase activity, apoprotein CII and apo E. These are covered in chapter four. Finally, scattered throughout the book are papers with recent insights in the molecular biology of apoprotein synthesis and metabolism. Here the molecular etiology of lipoprotein deficiency syndromes are explored at the genomic level.

This area will be of particular interest to those wishing to understand the molecular biology of lipoprotein disorders. We believe that this book will be of use to clinical lipigologists, resident trainees and research fellows as well as graduate students interested in both research and clinical aspects of lipoprotein metabolism.