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 and diabetes, we examined ob gene expression in KK mice and congenic lethal yellow obese KKA(y) mice. Northern blot analysis revealed that the ob mRNA levels are roughly equivalent in each of the epididymal, mesenteric, 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 and 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 hyperglycemia, hyperlipidemia, and hyperinsulinemia. The ob gene expression 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 unchanged in the subcutaneous WAT. The present study demonstrates that adipose tissue expression of the ob gene is regulated depending on the nutritional status in KK and KKA(y) mice.