Relationships between plasma lipoproteins and glucose in fasted chickens selected for leanness or fatness by three criteria.

In order to identify the mechanisms which underlie fattening in commercial birds, lean and fat broiler chickens have been selected according to 3 different criteria: abdominal fat content, plasma glucose level and plasma concentration of very-low-density lipoproteins (VLDL), the latter being the main substrate from which bird adipose tissues accumulate triglycerides. Chickens selected for high abdominal fat content displayed a higher level of VLDL and a lower level of glucose than their lean counterparts. Conversely, selection for high plasma VLDL or low plasma glucose resulted in 2 fat lines of chickens. The differences in intermediate- and low-density lipoproteins reflected a different balance in synthesis and catabolism of VLDL among the lines, whereas there was no difference in high-density lipoproteins. These data clearly demonstrate the relationship between lipid and carbohydrate metabolism and their role in the susceptibility to fattening. They suggest a greater use of carbohydrate for hepatic lipogenesis in fat chickens, resulting in a higher synthesis and secretion of VLDL and of their subsequent accumulation of triglycerides in the adipose tissue.