Type 2 diabetic Tsumura, Suzuki, obese, diabetes (TSOD) mice gradually gain weight as compared to corresponding Tsumura, Suzuki, non-obesity (TSNO) control mice, and develop insulin resistance. Although development of type 2 diabetes mellitus is associated with dysfunction of adipocytes, little is known about the properties of adipocytes from TSOD mice. Therefore, we attempted to remove intracorporeal factors and elucidate inherent properties of adipocytes of TSOD mice using adipocytes differentiated from mouse embryonic fibroblasts ( Key words adipocyte; differentiation; obesity; peroxisome proliferator-activated receptor-γ (PPARγ); rosiglitazone; Tsumura, Suzuki, obese, diabetes (TSOD) mouseThe worldwide population with type 2 diabetes mellitus (T2DM) is increasing, and the number of patients reached 415 million in 2015.1) Since T2DM is associated with vascular and other end-organ disease, 2) prevention of T2DM is a major public health issue. It is well known that obesity is a major risk factor for T2DM.3) Notably, incident of T2DM is correlated with abdominal visceral adipose tissue mass in humans.4) Therefore, understanding of roles of adipose tissue in the development of T2DM may lead to better methods for prevention of T2DM.Adipose tissue plays important roles in energy storage and release, and secretes various cytokines. Previous studies show that adipose-specific knockout of mitochondrial transcription factor A enhances energy expenditure and protects from dietinduced obesity and insulin resistance in mice.5) Moreover, adipose-specific glucose transporter type 4 (GLUT4) knockout mice exhibit insulin resistance and diabetes via secretion of retinol binding protein-4. 6) Thus, adipose functions are closely associated with the development of insulin resistance and T2DM. However, since T2DM is a complex illness resulting from a variety of genetic and environmental factors, single gene knockout mice provide limited information on the roles of adipose tissue in the development of T2DM. Therefore, more suitable model of human T2DM have been needed for such a kind of research.In 1992, the Tsumura, Suzuki, obese, diabetes (TSOD) mouse has been established as an animal model of human T2DM by the selective breeding of male mice of ddY strain with heavy body and urinary glucose.7) The mice exhibit overeating and gradually gain weight as compared to corresponding control mice, Tsumura, Suzuki, non-obesity (TSNO), and high blood glucose and urinary glucose are frequently observed in male mice of TSOD. Quantitative trait locus (QTL) analysis reveal that body weight and blood glucose levels in male mice of TSOD are affected by combination of multiple genetic loci (e.g., NIDD4,5,6).8) Several studies examine the roles of adipose tissue in development of T2DM using the mice and show that insulin-dependent glucose uptake 9) and GLUT4 translocation to the plasma membrane 10) is impaired in the adipose tissue. However, since these properties may be developed by various intracorporeal factors such as hormones and cytokines, t...