REGULATION OF OBESE GENE-EXPRESSION IN KK MICE AND CONGENIC LETHAL YELLOW OBESE KKA(Y) MICE

To elucidate the regulation of obese (ob) gene expression in obesity a nd diabetes, we examined ob gene expression in KK mice and congenic le thal yellow obese KKA(y) mice. Northern blot analysis revealed that th e ob mRNA levels are roughly equivalent in each of the epididymal, mes enteric, and subcutaneous white adipose tissue (WAT) from KK and KKA(y ) mice at 4 wk of age, when the obese phenotype of KKA(y) mice was not apparent. Expression of the ob gene was augmented in the mesenteric a nd subcutaneous WAT but was unchanged in the epididymal WAT in KKA(y) mice at 12 wk of age, when KKA(y) mice developed marked obesity with h yperglycemia, hyperlipidemia, and hyperinsulinemia. The ob gene expres sion was also examined during fasting in 12-wk-old KK and KKA(y) mice. After 24 or 72 h of fasting in both mouse strains, ob gene expression was downregulated in the epididymal and mesenteric WAT but was unchan ged in the subcutaneous WAT. The present study demonstrates that adipo se tissue expression of the ob gene is regulated depending on the nutr itional status in KK and KKA(y) mice.