Quantitative comparison of adipocytokine gene expression during adipocyte maturation in non-obese and obese rats

Adipocytokines secreted from adipocytes have been extensively analyzed due to their role as key factors in various complications of obesity, including arterial sclerosis, liver steatosis, insulin resistance, and diabetes. Several in vivo and in vitro studies have suggested that adipocyte maturation is related to fluctuations in adipocytokine secretion. However, the relationship between adipocyte maturation and adipocytokine levels has not been fully elucidated. Therefore, we sought to clarify the link between adipocytokine gene expression and adipocyte maturation through systematic analysis. We quantified mRNA for six adipocytokine genes: adiponectin, resistin, leptin, plasminogen activator inhibitor 1 (PAI-1), heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), and visfatin, in adipose tissue, in primary cultured adipocytes obtained from an obese Zucker rat, and in the preadipocyte cell line 3T3-L1. Moreover, to elucidate the role of adipocytokines in adipocyte maturation, adipocytokine expression levels were analyzed during maturation. Although fluctuations in adipocytokine gene expression were heterogeneous, gene expression was highly similar during maturation of primary cultured adipocytes from obese and non-obese rats, suggesting that the maturation process is independent from processes that lead to obesity. Moreover, the expression patterns of adiponectin, resistin and leptin mRNA in 3T3-L1 cells were highly similar to those in primary cultured adipocytes, indicating that these adipocytokines could be common maturation markers for primary cultured adipocytes obtained from obese and non-obese rats, and for preadipocyte cell lines.