Postnatal expression of adipose tissue metabolic activity associated with a porcine genetic obesity

To determine the age at which phenotypic expression of adipose tissue metabolic activities or adipocyte hypertrophy were detectable in a porcine obesity model, adipose tissue samples were obtained from genetically obese and lean pigs at 0, 7, 14, 21, 28, 42 and 56-d postpartum (weaning at 28 d). Adipocyte size was determined on osmium-fixed tissue slices using particle counter methods. Rates of glucose metabolism to CO2, total lipids and glyceride-fatty acids, as well as the basal and epinephrine plus theophylline-stimulated lipolytic rates were measured in tissue slices in vitro. Larger adipocytes were discernible in obese than lean pigs at birth and all subsequent postpartal ages. Expressed per cell, adipose tissue from obese pigs had greater glucose metabolism rates in vitro than that from lean pigs at 42 and 56 d; the rates were the same in obese and lean pigs at 28 d. Adipose tissue lipolytic rates in obese compared with lean pigs tended to be greater, were greater and were similar at 28, 42 and 56 d, respectively. These metabolic rates in vitro suggest that the early manifestation of the obesity evident as cell hypertrophy at birth and during early postnatal development is not the result of increased rates of adipose tissue glucose metabolism or decreased rates of adipose tissue lipid degradation.