In vertebrate animals, adipose tissue functions primarily to store excess energy in the form of triglycerides in periods of nutritional abundance and mobilize it in response to fasting (1 ,2 ). It also plays important roles in fatty acid metabolism and glucose homeostasis (3 ). Recently, adipose tissue has been shown to have endocrine functions by synthesizing and secreting a group of signaling molecules to regulate various body functions (4 –6 ). This is illustrated by the identification of ob gene product (leptin). Leptin is secreted exclusively from fat into the circulation and acts to regulate body weight, via a receptor (db gene product) in the cerebroventricular region of the brain (6 –9 ). Thus the ability to interact and regulate diverse functions in fat and other tissues represents a new facet of adipose tissue physiology.
