The Role of Apolipoprotein APO A-IV in Eating Behavior and Diet

Abstract

Apolipoprotein A-IV (apo A-IV) is a glycoprotein secreted together with triglyceride (Tg)-rich lipoproteins by the small intestine. In rodents, apo A-IV is secreted both in the intestine and the liver, the former being the major organ responsible for circulating apo A-IV. Intestinal apo A-IV synthesis is stimulated by fat absorption, and attenuated by intravenous leptin infusion. Intestinal apo A-IV secretion is also influenced by members of the pancreatic polypeptide family. Recently, apo A-IV has been found in hypothalamus, where it is regulated by food deprivation and lipid feeding. Several hormones, as long as nutritional status and circadian rhythms, appear to regulate apo A-IV synthesis and secretion both in the gastroenteric tract and in the hypothalamus. Central administration of neuropeptide Y (NPY) significantly increases apo A-IV mRNA levels. A role of apo A-IV in the regulation of food intake has been suggested and many evidences sustain this hypothesis. Many studies have provided information about the effects of a fat-rich diet or high-carbohydrates diet on apo A-IV concentration in animals. Inhibition of food intake by apo A-IV is mediated centrally and apo A-IV appears to be involved both in short and long-term regulation of food assumption. The main purpose of this chapter is to explain the role of apo A-IV in food intake regulation and illustrate future perspectives and unsolved problems in this field. Relation between apo A-IV and obesity, other metabolic diseases, pharmacological treatments for obesity, and dyslipidemia will be discussed too.