Tumor necrosis factor-α reduces adiponectin production by decreasing transcriptional activity of peroxisome proliferator-activated receptor-γ in calf adipocytes

Adiponectin (encoded by ADIPOQ) is an adipokine that orchestrates energy homeostasis by modulating glucose and fatty acid metabolism in peripheral tissues. During the periparturient period, dairy cows often develop adipose tissue inflammation and decreased tumor necrosis factor-a (TNF-a) plays a pivotal role in regulating the endocrine functions of adipocytes, but whether it affects adiponectin production in calf adipocytes remains obscure. Thus, the present study aimed to determine whether TNF-a could affect adiponectin production in calf adipocytes and to identify the underlying mechanism. Adipocytes isolated from Holstein calves were differentiated and used for (1) BODIPY493/503 staining; (2) treatment with 0.1 ng/ receptor-? (PPARG) small interfering RNA for 48 TNF-a for 24 h; and (4) overexpression of PPARG for mL TNF-a for 24 h. After differentiation, obvious lipid droplets and secretion of adiponectin were observed in adipocytes. Treatment with TNF-a did not alter mRNA abundance of ADIPOQ but reduced the total of mRNA abundance of endoplasmic reticulum (ER)/ forming oxidoreductase A-like protein (GSTK1) were downregulated in TNF-a-treated adipocytes, while 78-kDa glucose-regulated protein and Golgi-localizing ?-adaptin ear homology domain ARF binding protein-1 were unaltered. Moreover, TNF-a diminished nuclear translocation of PPAR? and downregulated mRNA abundance of PPARG and its downstream target gene fatty acid synthase, suggesting that TNF-a suppressed the transcriptional activity of PPAR?. In the absence of TNF-a, overexpression of PPARG enhanced the total and HMW adiponectin content in supernatant and upregulated the mRNA abundance of ADIPOQ, ERP44, ERO1A, and GSTK1 in adipocytes. However, knockdown of PPARG reduced the total and HMW adiponectin content in supernatant and downregulated the mRNA abundance of ADIPOQ, ERP44, ERO1A, and GSTK1 in adipocytes. In the presence of TNF-a, overexpression of PPARG decreased, while knockdown of PPARG further exacerbated TNF-a-induced reduc-tions in total and HMW adiponectin secretion and gene expression of ERP44, ERO1A, and GSTK1. Overall, TNF-a reduces adiponectin assembly in the calf adipo-cyte, which may be partly mediated by attenuation of PPAR? transcriptional activity. Thus, locally elevated levels of TNF-a in adipose tissue may be one reason for the decrease in circulating adiponectin in periparturi-ent dairy cows.

Automated summary

This study aimed to investigate the effect of TNF-a on adiponectin production in calf adipocytes and to identify the underlying mechanism. The researchers found that TNF-a reduced adiponectin production by attenuating PPAR? transcriptional activity. This suggests that locally elevated levels of TNF-a in adipose tissue may contribute to the decrease in circulating adiponectin in periparturient dairy cows.