[Development of esterification capacity of fatty acids in the adipocytes of the rat before weaning: the effect of milk overfeeding]. / Evolution de la capacité d'estérification des acides gras dans les adipocytes de rat avant le sevrage: effet de la suralimentation lactée.

ABSTRACT

During the suckling period, lipid storage in rat adipose tissue arises from exogenous triglycerides, as milk contains a large amount of lipid. In the present work, we studied the effect of overfeeding during the suckling period on the developmental pattern of the fatty acid esterification pathway in fat cells. Early overfeeding was induced by restricting litter size; at 2 days of age, the pups were randomly distributed to form litters of 4 (overfed group) or 8 (controls). During the suckling period the activity of lipoprotein lipase (LPL), glycerophosphate dehydrogenase (G3PDH), glycerophosphate acyl transferase (GPAT) and acyl CoA ligase were measured in isolated fat cells from the inguinal adipose tissue. As early as 10 days of age, plasma triglyceride levels were increased in overfed pups as compared to the controls and, in these animals, the adipose tissue was overdeveloped, mainly due to fat cell hypertrophy. At that age, overfeeding induced a significant increase in LPL and GPAT activities, but acyl CoA ligase and GPDH were not modified in overfed pups. Fat cell hypertrophy appeared to be responsible for the increased GPAT activity in the overfed pups. On the contrary, the effect of overfeeding on LPL activity was not only related to fat cell enlargement, as the enzyme activity continued to increase in the overfed rats when expressed per unit of cell surface area. These results show that overfeeding during the suckling period rapidly induced an increase in the fat storage capacity of the adipose tissue. This suggests that circulating triglyceride levels could regulate directly or through hormonal control the activity of the fatty acid esterification pathway in fat cells.