Differential depot-specific parameters of adipose tissue cellularity and thermogenesis in preobese congenic LA/Ntul//-cp rats

Abstract

To determine the effects of adipose tissue development during early normal postweaning growth, groups of lean and obese LA/N//tul-cp rats were subjected to measures of caloric intake, linear growth and of adipose tissue mass, cell lipid content, and adipocyte number in principle adipose tissue depots at 6 weeks of age, prior to the expression of significant adiposity. Live body weights and daily caloric intake of obese > lean by 6 weeks of age, but parameters of linear growth were similar in both phenotypes. Resting metabolic rate (RMR) and the thermic response to norepinephrine (NE, 200 µg/KG BW, s.c.) of lean >> obese rats. Adipose tissue mass and combined fat pad mass:body weight ratio of Dorsal Subcutaneous (DOR), Retroperitoneal (RP), Gonadal (GON), and Interscapular brown adipose tissue (IBAT) depots were greater in the obese than lean phenotype, with the greatest magnitude of increase in the DOR subcutaneous depot. Adipocyte number was modestly greater in DOR subcutaneous depot, while adipocyte lipid content was greater in the RP and GON depots of obese but not lean rats. The IBAT mass and proportion of IBAT:body weight of obese >> lean. These results are consistent with the differential onset of adipose tissue depot growth initially occurs via hyperplasia in the dorsal subcutaneous depot and via hypertrophy in the RP and GON abdominal depots, while lean tissue development was of similar magnitude in both phenotypes at this age.