NONSHIVERING THERMOGENESIS AND OBESITY IN THE DIABETIC WKY N-CP RAT/

Groups of lean and obese WKY/N-cp rats were fed a diet containing 54% carbohydrate, 20% protein, and 16% fat plus other essential nutrients from 1 until 8 months of age. Final body weights of obese were 1.7-fol d > lean littermates. The greater BW were associated with marked incre ases in adipocyte size, number/depot, and fat pad mass in all major wh ite adipose tissue depots. Interscapular brown adipose tissue (IBAT) m ass of obese was 3-fold > lean, and represented a greater proportion o f final body weight in obese than lean. The greater IBAT obese was due to greater lipid accretion and increased non-fat residue than occurre d in lean rats. Resting thermogenesis (RMR) of lean > obese. The therm ic response to norepinephrine was proportionately similar in both phen otypes, but the thermic response to cold (4 degrees C) of lean much gr eater than obese. Serum T4 concentrations and T4:T3 ratios of lean > o bese, while serum T3 concentrations were similar in the two phenotypes . These results are consistent with a decreased capacity for NST in th e obese phenotype of this stain, and suggest that the decreased NST ma y be due in part to alterations in BAT-mediated thermoregulation, in c ombination with impairments in other neuroendocrine or hormonal mediat ors of thermogenesis.